1. Field of the Invention
The present invention relates to improvements in rotary latches of the general type that employ at least one rotary jaw that is releasably retained in a latched position by a rotary pawl, wherein the rotary jaw and the rotary pawl extend principally within what can be referred to as a xe2x80x9cprimary planexe2x80x9d and pivot about separate parallel-extending axes that are substantially perpendicular to the primary plane, and wherein one or more torsion springs 1) extend principally within what can be referred to as a xe2x80x9csecondary planexe2x80x9d located beside and extending parallel to the primary plane, 2) bias the rotary jaw away from its latched position toward its unlatched position, and 3) bias the rotary pawl away from its jaw-releasing position toward its jaw-retaining positionxe2x80x94with improvements residing in the manner in which one or more end regions of the torsion springs are coupled to one or both of the rotary jaw and the rotary pawl by connections located principally within the secondary plane. More particularly, the present invention relates to improvements that enhance the service longevity of rotary latches and locks of the general type disclosed in U.S. Pat. Nos. 5,884,948, 5,611,224, 5,595,076, 5,586,458, 5,564,295, 5,439,260, 5,117,665, 5,069,491, 4,917,412, 4,896,906, 4,320,642 and 4,312,203 (referred to hereinafter as the xe2x80x9cRotary Latch Patents,xe2x80x9d the disclosures of which are incorporated herein by reference), by providing stress-diminished spring-to-rotary-jaw and spring-to-rotary-pawl connections that utilize C-shaped curve formations defined on end regions of the torsion spring or springs that open outwardly away from coils of the torsion spring or springs, wherein the C-shaped curve formations and peripheral portions of the spring coils are engaged by smoothly curved formations of the rotary jaw and/or the rotary pawl that extend from the primary plane into the secondary plane to establish the improved connections within the secondary plane in a manner that causes no twisting of the torsion springs when forces are transmitted between the torsion springs and the rotary jaw and/or rotary pawl to which the springs are coupled by the improved connections.
2. Prior Art
The Rotary Latch Patents referenced above disclose a variety of latch and lock products, each of which utilizes a rotary jaw that is biased by a torsion coil spring away from a latched position toward an unlatched position, and a rotary pawl that is biased by the same or a separate torsion coil spring away from a jaw-releasing position toward a jaw-retaining position. The rotary jaws and the rotary pawls of these units have engageable formations that cooperate to enable the rotary pawl to retain the rotary jaw in, and to release the rotary jaw from the latched position by pivoting the rotary pawl into and out of the jaw-retaining position.
Other features shared by rotary latch and lock units of general type disclosed in the Rotary Latch Patents include 1) the manner in which each of these units positions torsion coils of one or more torsion springs to extend in a secondary plane located beside and substantially paralleling a primary plane in which the rotary jaw and the rotary pawl extend, and 2) the manner in which connections are formed between end regions of the torsion springs and the rotary jaws and pawlsxe2x80x94connections that utilize bent spring end formations that extend transversely out of the secondary plane and into the primary plane to hook across portions of the rotary jaws and pawls. To provide spring end formations that extend smartly across and that hook smartly onto portions of the rotary jaws and pawls, it has become quite customary to introduce relatively sharp bends into the spring end regionsxe2x80x94essentially xe2x80x9cright-angle bendsxe2x80x9d that are located at opposite ends of reaches of spring material that extend transversely across and hook onto the jaws and pawls.
While rotary latch and lock units of this type ordinarily offer lengthy service lives, it is important to work toward enhancing the service life longevity of these units by observing which components tend to fail the earliest, and by finding ways to improve the units to eliminate these early failures. Extensive testing has shown that, especially in the presence of excessive vibration, early failures can occur in the torsion springs of these unitsxe2x80x94failures that tend to be located within the vicinity of where a first right angle bend is used to connect a torsion spring coil to a reach of spring material that extends transversely out of the secondary plane into the primary plane to hook around rotary jaw or pawl portions located within the primary plane.
Most of these spring failures occur near right angle bends in torsion spring end regions that connect with rotary jaws, with a far fewer number of failures occurring near right angle bends in torsion spring end regions that connect with rotary bawls. The fact that more jaw-spring failures have been noted than pawl-spring failures makes sense inasmuch as the rotary jaws pivot through a much wider range of angular movement than do the rotary pawls (which puts more stress on torsion spring portions that connect to the rotary jaw than is experienced by torsion spring that connect with the rotary pawl), and inasmuch as the rotary jaws and the spring portions connected thereto often are subjected to sudden impact forces that come as the result of slamming a strike formation directly into engagement with a rotary jaw to pivot the jaw quickly from its unlatched position to its latched position (whereas rotary pawls and spring portions connected thereto are seldom subjected to sudden and severe impact forces of this type).
If one studies the region of the first right angle bend (where a torsion coil is connected by a right angle bend to a reach of spring material that extends transversely out of the secondary plane across the primary plane to hook around portions of a rotary jaw or pawl), what becomes apparent is that, in the vicinity of this bend, twisting forces are applied to the spring as the transversely extending reach is utilized to transmit forces between the torsion coil and the rotary jaw or pawl. This twisting of the spring in the vicinity of the first right angle bend causes greater stress to occur in the vicinity of the first right angle bend than occurs elsewhere in the springxe2x80x94and the result, quite naturally, is that the spring tends to break in the vicinity of the first right angle bend after extensive cycles of use or in the presence of severe vibration.
Still another factor that may contribute to early spring breakage within the vicinity of right-angle bends has to do with stresses that may be introduced into a spring in the vicinities of its right angle bends when the spring is formed. The tighter the bend that is formed in a piece of spring wire, the greater is the tendency to introduce unwanted stresses in the vicinity of the bend.
It is well established that even small but cost effective improvements in rotary latch and lock units of the type disclosed in the referenced Rotary Latch Patents tend to gain quick acceptance in industry. There are millions of rotary latch and lock units of this general type presently in service, and the replacement of broken, damaged or disabled units with units that offer enhanced service longevity is a serious ongoing undertaking. In this vein, the improvement features offered by patents such as U.S. Pat. No. 5,884,948, for example, have gained rapid acceptance in industry by providing enhanced service longevity in rotary latch units of relatively low cost.
An important consideration to be taken into account when improvements are provided in rotary latch and lock units of the type disclosed in the referenced Rotary Latch Patents is the fact that the improved units need to offer interchangeability with units that are already in servicexe2x80x94so that, when improved units are installed to replace broken, damaged or disabled units, the replacement units will offer size and configuration interchangeability with the units they replace, otherwise the installation of the replacement units would be rendered unduly difficult, and other components that are located near the replaced latch units might need to be repositioned or restructured.
Still another important consideration is the normally higher cost of replacement units that offer enhanced service longevity. Whereas present-day units are formed utilizing simple wire-wound springs and stamped jaw, pawl and side plate components, life-enhanced units may employ more costly components. The improvements they offer in service longevity need to justify any added costs that result.
A further consideration to take into account if present-day rotary latch products are to be provided with improvements is a need that sometimes arises, for example in automotive applications, for rotary jaws to be provided with boot-like protective rubber or elastomeric coatings that cover striker-engaging portions of the jaws to help silence latch operation. The jaws of most present-day rotary latches carry no formations that are well suited to assist in holding boot-like protective rubber or elastomeric coatings in place; hence, when rubber or elastomeric coatings are applied to the jaws of present-day latches, it is often found that they slip off (in much the same way that a pair of low-cut overshoes can slip off quite easily from shoes on which they have been installed).
The present invention provides a number of improvements relating to rotary latches of the general type disclosed in the referenced Rotary Latch Patents, including a way in which non-right-angled hook-like connections evincing significantly improved service life longevity can be provided between a rotary jaw (or a rotary pawl) and a torsion spring end region that connects therewith. Since breakage of jaw connected springs is what most often disables a rotary latch or lock, improving the spring-to-jaw connection is a major thrust of the present invention; and, such other improvements as may be provided to accompany this significant improvement are considered optional but well worth considering when new rotary latch and lock products are manufactured.
In one form of the present invention, a rotary latch includes a rotary jaw and a rotary pawl that are mounted for limited pivotal movement about separate substantially parallel-extending axes, wherein the rotary jaw is pivotal between a latched position and an unlatched position, and wherein the rotary pawl is pivotal between a jaw-retaining position wherein a jaw-engageable portion of the rotary pawl is engageable with a pawl-engageable portion of the rotary jaw to retain the rotary jaw in the latched position, and a jaw-releasing position wherein the jaw-engageable portion of the rotary pawl disengages the pawl-engageable portion of the rotary jaw and thereby permits the rotary jaw to pivot from the latched position to the unlatched position. The rotary jaw also includes a strike-engageable portion adapted to latchingly engage a strike formation when the rotary jaw is in the latched position, and to release the strike formation for movement toward and away from the rotary jaw when the rotary jaw is in the unlatched position. The jaw-engageable portion, the pawl-engageable portion and the strike-engageable portion all extend within a primary plane that is substantially perpendicular to the parallel-extending axes about which the rotary jaw and the rotary pawl pivot.
The rotary latch also includes biasing means for biasing the rotary jaw away from the latched position toward the unlatched position, and for biasing the rotary pawl away from the jaw-releasing position toward the jaw-retaining position. The biasing means includes at least one torsion spring having at least one torsion spring coil that surrounds at least one of the parallel-extending axes, and having and at least one reach of spring material that extends from a peripheral portion of the spring coil to define a C-shaped hook formation. The torsion spring coil, the reach of spring material and the C-shaped hook formation all extend within a secondary plane located beside and substantially paralleling the primary plane.
The rotary latch also includes means for engaging the peripheral portion of the torsion spring coil and the C-shaped hook formation to establish a connection between the torsion spring and a selected one of the rotary jaw and the rotary pawl, including a first connection portion of the selected one of the rotary jaw and the rotary pawl that extends transversely from the primary plane into the secondary plane to define within the secondary plane a first surface that is positioned to extend along a length of the peripheral portion adjacent the reach of spring material that defines the C-shaped hook formation, and a second surface that joins smoothly with the first surface to define a convexly curved C-shaped formation that substantially matches the shape of and is adapted to be received within the C-shaped hook formation. By this arrangement, a connection residing in the secondary plane is established between the torsion spring and the selected one of the rotary jaw and the rotary pawlxe2x80x94a connection that does not cause twisting of the torsion spring when forces are transmitted between the spring and the selected one of the rotary jaw and the rotary pawl.
In preferred practice, the first surface is, in fact, a curved surface that has substantially the same curvature as the peripheral portion of the torsion coil spring; the second curved surface joins smoothly with the first curved surface; and the first curved surface is positioned to engage a length of the peripheral portion adjacent the reach of spring material that defines the C-shaped hook formationxe2x80x94an arrangement that further assists in providing a stress-minimized, breakage resistant connection.
Other optional features can be included in rotary latch and lock units that embody the invention. If the first connection portion is provided on the rotary jaw, the first connection portion can include portions that enlarge the cross-sectional area of the second U-shaped notch defined by the rotary jawxe2x80x94so as to increase the area of the rotary jaw that engages the strike formation when the rotary jaw is latched. Increasing this area of engagement (i.e., increasing the effective thickness of the rotary jaw in the region that engages the strike formation) reduces wear on the rotary jaw caused by its engagement with the strike formation, and reduces wear on the strike formation caused by its engagement with the rotary jaw inasmuch as a more even distribution of load is achieved when larger surfaces areas of the strike formation and the rotary jaw engage each other.
An important advantage that results when the improvement features of the present invention are applied to the rotary jaw is that spring breakage in the area where the torsion spring connects with the rotary jaw is significantly diminished, and tends to occur only after a much longer service life, especially in the presence of excessive vibration. Tests have documented a considerable improvement in service longevity.